As I get better at the game, I'm often disappointed by my old builds, but I get so attached to the animals I breed. So instead of starting new zoos, I've been "renovating" the first big zoo project I ever tried to do. It's on its third incarnation now, and thinking of it as a renovation really helps me immerse myself and stay motivated-- I'll even write up short little role playing updates, where I explain to myself where the old animals are staying while the zoo is remodeling, how the newly-added animals are doing, and what my plans for the future are. I wasn't very good at building when I first started, and my habitats didn't look the greatest, so it's easy to pretend, now that I've improved, that the zoo is getting grants and donations to splurge on more extravagant construction versus the original, lower-budget look.
When I feel short on creativity, I try to look for more unconventional inspiration. There's a new ferry terminal in my state, in a building style I've been trying to incorporate into my zoo-- even though it's a ferry terminal, I used it as inspiration for the entrance of my zoo. And sometimes when I go to restaurants or shops, I take pictures of the buildings I like. There's a local REI store that I looks amazing as a primate house when you try to recreate it in-game lmao.